The invention relates to a chute feed which receives fiber tufts, forms them into a compacted matt, and discharges the fibers in the form of a fiber batt having a prescribed weight per unit length. The chute feed typically is utilized to feed the batt to a carding machine which separates out the immature, very short fibers and aligns the useful longer fibers into an opened, more parallel orientation as a web which is then drawn off in the form of a sliver strand or a web for, respectively, forming yarn or non-woven fabric.
The quality of the sliver or web produced by the card can depend largely upon the quality and uniformity of the fiber batt discharged by the chute feed. A high quality fiber batt usually is quite uniform in bulk density across its width to provide a desired consistent prescribed weight per unit length of the batt.
The chute feed typically includes a lower batt formation chute having a feed roll for feeding fiber into the chute, and a pair of delivery rolls which discharge the fiber batt. There is an upper fiber tuft reserve chute which receives and accumulates fiber above the feed roll. The feed roll then feeds these fibers to an opening roll which opens the fiber tufts by subdividing the tufts and delivers them to the batt formation chute. Optionally, an oscillating plate compacts the fibers in the batt formation chute to discharge a fiber batt having a prescribed weight. For this, the weight of the batt formed by the chute feed may be sensed and a signal representative of the sensed weight may be generated to control the speed of oscillation of the plate.
The quantity of fiber in the batt formation chute also may be sensed and used to control the operation of the feed roll and hence the influx or receipt of fiber into the batt formation chute. The feed roll typically is operated intermittently, which is to say, "on" and "off," in response to sensing fiber by some level sensor in the chute such as a photocell. The feed roll stops or rotates in response respectively to the presence or absence of fiber at the level monitored by the photocell. This intermittent operation may result in fluctuations in the feed of fiber to an impermissible degree forming cyclic "thins" and "thicks" in the fiber batt produced over the time period of operation.
A control system for a chute feed is disclosed in U.S. Pat. No. 4,387,486 wherein the speed of the card is sensed to generate a signal used to control the speed of the feed roll motor and also of the oscillation plate motor in a continuous manner. The weight of the batt received by the card is sensed and a representative signal is utilized to override the primary drive for the oscillating plate to change its speed and thus to vary the ratio between the speed of the card and speed of the plate. The level of fiber in the formation chute is sensed and a signal is generated which is used to override the primary signal to the feed roll to vary the speed of the feed roll and thus the ratio between the speed of the card and the speed of the feed roll.
U.S. Pat. Nos. 4,403,374; 4,404,710; 3,728,759; and 3,169,664 utilize air pumps and fans to compact fibers in a chute of a feed chute. In U.S. Pat. No. 4,404,710 the weight of the fiber batt is sensed and a signal generated which controls the operation of the air blower and the top feed roll.
U.S. Pat. No. 3,169,664 discloses a level sensor which controls the "on" and "off" operation of a feed roll for maintaining the fiber level at or below that of the sensor in a chute feed. Air pressure compacts the fibers and increased air pressure is provided when the carding machine is started.
While U.S. Pat. No. 4,387,486 provides a suitable control system for operation of a feed chute in response to the operation of a standard width carding machine, the advent of the modern wide carding machines, up to four meters in width, may create problems with conventional control systems. Moreover, it is desirable to provide a chute feed which is synchronized in a self-contained manner and may be easily utilized with associated machinery other than a carding machine operation. Regarding the wide carding machines, it has been found that under certain adverse conditions, the level or volume of the fiber may continue to build unduly in the chute due to its extreme width and that adequate control need be provided. In certain other instances, it may prove necessary to provide yet additional compaction of the fibers beyond what is possible by the normal operation range of the oscillating plate in the wide carding machines due to their large chute volumes.
It may also prove to be desirable to be able to modify continuous feed roll operation and control the feed roll intermittently at certain low speeds of the delivery roll, such as during card start-up, in order to obviate feed of non-uniform weights of fiber tufts. When the speed of the bottom delivery rolls falls below some certain value, a too slow rotation of the feed roll may result in feeding nonuniform weights of fiber tufts per unit time to the batt formation chute. However, by operating the feed roll intermittently but at speeds above this too slow speed, nonuniform tufts may be prevented without excessive feed of fiber and the undesired oversupply.
Accordingly, an objective of the present invention is to provide a control system for a feed chute by which a fiber batt having a uniform bulk density across its width is produced under normal operation of the feed chute.
Another object of the present invention is to provide a control system for a chute feed where the speeds of the feed roll and the oscillating compaction plate of a batt formation chute are synchronized in operation with the rotational speed of a delivery roll, and other factors caused by the large width of the chute in the range of three to four meters are taken into affect.
Still another object of the present invention is to provide a control system for a chute feed having a batt formation chute with a fiber feed roll and an oscillating fiber compaction plate wherein fiber compaction may be automatically augmented by compressed air as desired.
Yet another object is to provide the aforesaid control system wherein fiber compaction may be automatically augmented by compressed air as desired, and wherein the speed of the feed roll is automatically controlled in response to signals generated upon attaining conditions of an oversupply of fibers in the chute or a too slow delivery roll speed to terminate fiber feed.